Magneto ventilation system



May 21, 1957 Filed March 51, 1955 2 Sheets-Sheet l lNl/ENTOR HMER 6. MEKHAEFER ahia/2L4.

ATTORNEY May 21, 1957 c, KlEKHAEFER 2,792,821

MAGNETO VENTILATION SYSTEM Filed March 31, 1955 2 Sheets-Sheet 2 INVENTOR. ZMMH? C MHWEFHP A 7'7'ORNEY United States Patent MAGNETO VENTILATION SYSTEM Elmer C. Kiekhaefer, Cedarburg, Wis.

Application March 31, 1955, Serial No. 498,323

2 Claims. (Cl. 123-198) This invention relates generally to magneto ventilation systems and more specifically to an improved ventilation system for the magneto of an outboard motor.

Outboard motors have heretofore been provided with a cowl interposed between the power head and the drive shaft housing to prevent the entry of water and spray into the power head. The cowl has generally been constructed to be substantially air tight, the only opening therein being a small air opening large enough to admit a sufiicient quantity of air into the power head for combustion purposes. In an outboard motor equipped with this type of cowl, there is the disadvantage that a mixture of gas and air will accumulate within the cowl as a result of blow-back and gas leakage out of the carburetor, and this mixture of gas and air if correctly proportioned will explode when ignited by a spark from the magneto.

Certain types of magneto ventilation systems have been used in the past, but none suited to eliminate the possibility of an explosion within the cowl. All of the prior systems have an air pressure developed within the magneto that is less than the air pressure within the cowl. This has the disadvantage that any explosive gas-air mixture within the cowl may be forced into the magneto through openings between the housing, end cap and distributor cap of the magneto, particularly when the magneto parts do not form an air tight assembly, resulting in an explosion damaging the power head and possibly injuring the operator thereof.

It is therefore an object of the present invention to provide an improved magneto air vent means for an outboard motor which eliminates the explosive and fire hazard resulting from the accumulation of gas and air mixture within the cowl.

Another object of the invention is to provide an improved magneto ventilation system for an internal combustion engine enclosed in a cowl wherein the pressure developed within the magneto is greater than the air pressure within the cowl.

Another object of the invention is the provision of an improved magneto air vent for an outboard motor that permits the use of a cowl that is substantially air tight.

Another object of the invention is the provision of an improved magneto ventilation system wherein the manufacturing of the parts of a magneto to close tolerances is eliminated as well as the need for sealing means therebetween.

Objects and advantages other than those set forth above will be apparent from the following description when read in connection with the accompanying drawing, in which:

Fig. 1 shows a side elevation view of an outboard motor in which applicants invention is embodied;

Fig. 2 is an enlarged fragmentary elevation view in section of a part of the outboard shown in Fig. 1 embodying the invention;

Fig. 3 is a side elevation view in section of the magneto shown in Fig. 2;

Fig. 4 is a section view taken along line 4--4 of Fig.2

Z ,7 952,852 1 Patented May 21, 1957 showing the inlet and outlet openings formed by the cowl; and

Fig. 5 is a front elevation view partly in section of the structure of Fig. 1 showing the air inlet opening into the cowl and the air inlet and outlet openings in the cowl connecting the magneto ventilation system to atmosphere.

As shown in the drawings, a preferred embodiment of this invention is illustrated as applied to an outboard motor 1 having a power head 2 mounted on a drive shaft housing 3. A substantially air tight cowl 4 is provided for the power head 2 and has a lower part 6 in the form of a generally upwardly dished member mounted between the drive shaft housing 3 and the power head 2. The lower part 6 is provided with an annular flange 7 along the upper edge thereof. The upper part 8 of the cowl 4 V p is mounted to the power head 2 and forms a cover therefor, and is also provided with an annular flange 9 along the lower edge thereof in registry with the annular flange 7.0f the lower part 6 and spaced vertically therefrom. An intermediate part 11 of the cowl 4 which is rectangularly shaped is wrapped around the power head 2 with the lower and upper edges thereof supported by the flanges 7, 9 and mating therewith to enclose and protect the power head 2. The ends 10 of the intermediate part 11 are spaced apart as shown in Fig. 5 to form an air inlet opening 15 for the cowl 4, and the part 11 is clasped together onto the flanges 7 and 9 of cowl portions 6 and 8 by suitable clamping means 16. The cowl 4 forms the subject matter of a co-pending application, Serial No. 455,492, now Patent 2,756,736, issued July 31, 1956, and is more fully explained therein.

The electrical ignition system for the outboard motor 1 comprises a magneto 12 for generating the current for the electric ignition system as is well known in the art. In the generation of the current for the ignition system, the

v high potential current flashes or sparks passing between the distributor rotor contact and the successive distributor contacts controlling the current flow to the spark plugs of the engines cylinders, apparently breaks down the surrounding air and generates nitric oxide and ozone fumes in substantial amounts. In an outboard motor 1 having a relatively air-tight cowl 4, the explosive mixture formed within the cowl 4 may be readily ignited by this high potential spark.

The magneto 12 is formed essentially of a housing 13, an end cap 14 mounted on the housing 13 by any suitable means such as screws, not shown, and a distributor cap 17 mounted on the end cap 14 by any suitable means. The housing 13 and end cap 14 carry a magneto shaft 18 upon which is mounted a rotor 19 adapted to coact with a coil 21 upon rotation of the magneto shaft 18. The end cap 14 and distributor cap 17 form a cavity 22 within which the distributor rotor 19 is disposed and mounted on the end of the magneto shaft 18 for rotation therewith. Breaker points 23 are carried by the end cap 14 actuable by a cam 24 mounted on the magneto shaft 18. During rotation of the magneto shaft 18, the distributor rotor 19 acts as a centrifugal blower, expelling the air and gases out of the distributor housing 13.

In the ventilation system of this invention, the housing 13 and end cap 14 are provided with tapped openings 26, 27 respectively into which threaded ends of respective fittings 28, 29 are tightly screwed. The other end of each of the fittings 28, 29 is provided with a hose engaging portion 31, 32. A lower cowl member 6 also forms tapped openings 33, 34 therethrough into which the threaded ends of fittings 36, 37 similar to the aforementioned fittings 28, 29 are tightly screwed. A pair of flexible conduits 38, 39, shown as rubber tubes, each have one end fastened to the hose engaging end of the fittings 36, 37 respectively and the opposite end connected to the corresponding 3 hose engaging end .31, .32 of the .fittings ,28, 29. The flexible hoses 38, 39 are provided with suflicient length to permit rotational movement of the magneto 12 for the properadvance and retard of the spark. f

In operation, the movement of the outboard motor 1;in a forward direction coupled with the action ofthexdistributor rotor 19 as a centrifugal blower causes fresh "air to be forced through a closed ventilation system as shown in part in Fig. 3 by arrows comprising the atmosphere, opening 33, hose 38, housing 13,rcavity 22, hose 39, and tapped opening 34 back to atmosphere. The air pressure developed within the magneto 1.2. is consequently at a higher value than the air pressure within .thercowl 4-which is lower than atmosphere due to the pressure :drop .developed across the air inlet thereto so that any .airmovement through leakage cracks in themagneto .12 would be outwardlyytherefrom rather than inwardly, ithereby eliminatingthe likelihood of. an explosive gasair.mixture seepinginto themagneto 12 and causing anexplosiomwithin the cowl 4.

Although but oneernbodiment has been illustrated and described, .it will be apparent to thoseskilled .in theart that various changes and modifications of the invention may be made without departing from thespirit of the invention or from the scopeof :the appended claims.

It is claimed and desired .to secure byLetters Patent:

1. In a magneto ventilation system for aninternal combustion engine, the combination of: a magneto carried by said engine and having a housing with first air inlet and outlet openings; a substantially air tight cowl .enclosing said engine and provided with an air opening therethrough for admitting combustion air to said engine during operation at a pressure below atmospheric, said combustion air within said cowl contacting gas leakage from the engine carburetor to form an explosive gas-air mixture therein; a portion of said cowl further having second air inlet and outlet openings connecting the interior of said cowl to atmosphere and corresponding to said first air vinlet and outlet openings respectively; and conduit means connecting said first air inlet and outlet openings to said second airtinlet and outlet openings respectively 4 to form a magneto ventilation path to atmosphere, the pressure within the housing of said magneto being at a higher pressure than the pressure of said combustion air whereby air movement of said combustion air within said cowl into said magneto is prevented.

2. In a magneto ventilation system for an outboard motor having an internal combustion engine enclosed within a substantially air tight cowl in which air in contact with gas leakage from the engine carburetor forms an explosive gas-air mixture which during engine operation is at a pressure below atmospheric, the combination of: a magneto carried by said engine and having aihousing provided with a first threaded inlet opening and a first threaded outlet opening; a front portion of said cowl provided with a second threaded inlet opening and a second threaded outlet opening, each of said second openings connecting the interior of said cowl to atmosphere; a plurality of substantially L-shapedfittings, each of said fittings .having a threaded end and a hose engaging .end with said threaded end threadedly engaging one .of said first and second openings; and conduit means including 'a first flexible hose having one end connected to the hose engaging end of said fitting threaded into said first inlet opening and the other end connected to the hose engaging end of said fitting threaded into saidsecond inlet opening and a second flexible hose having one end connected to the hose engaging end of said fitting threaded into said first outlet opening and the other end of said second hose connected to the hose engaging end of said fitting threaded into said second outlet opening to form a magneto ventilation path to atmosphere with the pressure within the housing of said magneto being at a higher pressure than the pressure of said explosive gas-air mixture whereby movement of said mixture into said magneto is prevented.

References Cited in the file of this patent UNITED STATES PATENTS 1,813,808 'Kuehn July 7, 1931 1,921,427 Nowowielski Aug. 8, 1933 2,286,233 Scott June 16, 1942 

